Turbine blade



Jan. 21, 1 936. wETT$TE|N 2,028,533

TURBINE BLADE Filed Jan. 25, 1934 "2 Sheets-Sheet 1 1 L ly/ Jan. 21, 1936. F. A. WETTSTEIN 8,

TURBINE BLADE Filed Jan. 25, 1934 h 2 Sheets-Sheet 2 t/am WM Patented Jan. 21, 1936 v PATENT OFFICE TURBINE BLADE Fritz Alexander Wettstein,

Aktiebolaget a corporation of Sweden signer to Sweden,

Lidingo Sweden as- Spontari, Stockh olm,

Application January 25, 1934, Serial No. 708,290

In Germany February 3, 1933 '13 Claims. (01. 253-47) This invention relates to radial admission steam or gas turbines, the moving blades of which extend, in the form of a catenary-like curve, between axially spaced fastening rings, the object being to so shape theblades, which consist of elements of sheet material, as to effect a particularly efiicient utilization of the energy of the impelling means flowing therethrough, and to eliminate or minimize blade oscillation, evenin the case of thin sheet metal blades. This is accomplished, in accordance with the invention, by giving to curved configuration by pressing, drawing, hammering or the like.

The blades, which are preferably formed of sheet metal and generally of the type disclosed in U. S. Patent No. 1,942,608, may, of course, be relatively rigid, or they may be made of sheet metal of such thinness that they assume their catenary-like curve fluence of centrifugal force. ent that the sheet metal strips may be of uniform or varying thickness and/or of uniform or varying width, all of which has been disclosed in the aforementioned patent.

accordance with the invention andillustrated in Figs. 18 of the accompanying drawings wherein Fig. 1 is a side view of a portion of the blade nm;

Fig. 2 is a front view of one of the blades; v Fig. 3 is a top view, of the same blade;

Figs. 4 and 5 are sections taken tangentially to and radially of the blade ring;

Fig. 6 corresponds to Fig. i but ved blade-retaining grooves; and

Figs. 7 and 8 illustrate another embodiment of the invention.

In the drawings, reference character 2 designates a portion of a blade supporting or carrier ring, which is provided with attaching grooves 3 for the sheet metal blades l6, which are disposed between the supporting rings in catenary curvelike manner. The blades may be retained in the grooves 3 by means of the enlarged straight ends 4 of the dovetailed blade roots, and may be secured therein in any suitable manner. The blade rings are interconnected, in conventional manner, by means of struts in part supported by intermediaterings 6.

Blade carrying ring 2 is bounded, radially outillustrates wardly thereof, by surface 1 which may, for exthe blades a transversely to the application of configuration under the in- It is also appar-- with. the blades of 5 (Fig.2), which are ample, be a cylindrical or conical surface, into which the securing grooves 3 gradually merge, as is apparent from Figs. 2, 3 and 4. After the blades have been inserted into the grooves, packing or looking pieces 8 are packed into the blade 5 grooves at both ends of the blade roots in conventional manner, these pieces functioning to secure the blades longitudinally .of the grooves. However, as a result of their manner of attachment, the blades may be capable of a certain amount of transverse movement. For further, details as to the manner in which the blades may be secured to blade carrier 2 reference is made.

Fredrik Ljungstrom, Serial No. 708,300, filed January 25, 1934.

Before being inserted into the grooves, the blades are preferably ground to suitable thickness, and. are brought to their transversely curved configuration by pressing or drawing over a form or by hammering. To facilitate formation of said configuratiomit is desirable to harden the middle portion thereof, which possesses the maximum curvature, to a lesser extent than the blade ends. For example, the middle portion of the blade may be annealed so as to enable the requisite degree of deformation thereof to be effected during drawing, or the drawing may be carried .out prior to hardening of the blade.

The transversely curved configuration of the blades is indicated on the drawings by lines l8, l9 and 20. Lines I8 represent the intersections planes passing through the rotary axis. Lines is of Fig. 3 represent intersections with the blades of planes parallel to the plane of the drawing. Lines 20 of Fig. 1 represent intersections with the blades of planes perpendicular to the axis of rotation. Thus the blades are curvilinear in section in three right angularly related planes. In the illustrated embodiment, the transverse curvature of the blades is greatest in the middle and decreases gradual- 1y toward the blade ends, so that the ends of theblades maybe straight for insertion into rectilinear grooves 3. However, it is apparent that the transverse curvature of the blades may also extend to the blade ends, in which case it is necessary to impart a corresponding curvature to the securinggrooves as shown at 24in Fig. 6. Since the blades are made of sheet metal, they may be easily inserted sired curvature; consequently, the curvature of the grooves need not necessarily be along an arc of a circle. With this construction, the curve.- ture of the grooves and blade roots may corre- 1 spond to the desired direction of flow of the steam into grooves of any de- 50 configuration makes it ends of the sheet metal blades into the grooves.

The transverse curvature of the moving blades is advantageous in that it enables the number of blades to be considerably decreased in comparison with the numbers of sheet metal blades required by prior constructions, since the curved possible to obtain the optimum blade angle throughout; Preferably, r the blade angle is maintained constant over the entire width of the blades. Since the steam or gas flows through the blade rim along involutelike curves, corresponding to lines 20 in Fig. 1, the curved configuration of the blades represents the optimum shape for the fiow of the impelling means and, because of the small number of blades, effects an appreciable decrease in the so-called edge losses at the edges of the blades, which losses are often considerable. Finally, the decreased number of blades makes it possible to construct each individual blade and groove with greater care than heretofore, without increasing the cost of manufacture of the new blade rim over that of prior blade rims.

Furthermore, the curved character of the'sheet metal blades imparts a certain degree of rigidity thereto, even in the case of very thin sheet metal, which results in an increased capacity to resist oscillation and fluttering. Because of the reduced number thereof, the blades are of a comparatively large width, which also tends to stiffen and stabilize the blades. Finally, additional damping of oscillation may be effected by extending the blade roots of each pair of blades in adjacent grooves beyond each other, as shown in broken lines in Fig. 1, resulting in the formation of large overlapping surfaces between adjacent blade ends; It is preferred to make the walls of the resultant passageways for the impelling medium between adjacent blades parallel to each other; however,this is not essential. It is obvious that the shape of the overlapping surfaces may be changed from that shown in Fig. 1 by changing the proportions of the blades. For instance, the width of the overlap may be changed toward the blade ends or may be maintained constant along the entire length of the blade.

Finally, it is possible to impart a double curvature to one or both of the front and rear edges of the blade of such character that the front edge 22 (Figs. '7 and 8) will be concave and the rear edge 23 convex, in side view. These curvatures may be produced by providing the front and rear edges of the sheet metal strips used in making the blades with punched out arcuate curves as shown in Fig. 8. The resultant double' curved blade edges present the advantage that the catenary-like curve produced by centrifugal force becomes somewhat narrower at the front edge than at the rear edge, which may be favorable to the shape of the passageway defined between the blades.

It will be obvious that the invention is not limited to the specific blade shown in the drawings, but is capable of a variety of mechanical embodiments. While the drawings illustrate a preferred form of the invention, it is to-be expressly understood that these drawings are for the purpose of illustration only and are not to be construed as defining the limits of the invention since various changes, which will now be apparent to those skilled in the art, may be made in the shape, size and arrangement of the blades without departing from the inventive concept. So, for instance, a blade of a comparatively large width may or gas and still permit the easy insertion of the be'formed by combining two or more transversely curved blade elements of a smaller width, the edges of which are joined together in any suitable manner, as by soldering, welding or the like. Reference is therefore to be had to the appended 5 claims for a definition of the limits of the invention.

What is claimed is:

1. A turbine blade comprising a member of sheet material having the form of a catenary- 10 like curve between its ends and curvilinear in section in three right angularly related planes.

2. A turbine blade comprising a member of sheet material which is curved to be catenarylike between its ends and has involute curvature 15 in transverse planes at right angles to a line joining the ends of the blade.

3.,A turbine blade comprising a member of sheet material having the form of a catenarylike curve between its ends and curvilinear in sec- 20 tion in three right angularly related planes, said transverse curvature being greatest at a point midway between the blade ends and gradually decreasing toward said ends.

4. A turbine blade comprising a member of 25 sheet material having the form of a catenarylike curve between its ends and curvilinear in section in three right angularly related planes, said transverse curvature being greatest at a point midway between the blade ends and dis- 30 appearing gradually toward said ends, the latter being rectilinear.

5. A turbine blade comprising a member of sheet metal having the form of a catenary-like curve between its ends said transverse curvature being such that the lines of intersection of said blade with planes perpendicular to a line joining the blade ends are involute-like in character and with planes parallel to said line 6. A blade rim for radial admission turbines comprising axially spaced rotatable blade carrying rings, and blades anchored at their ends to and extending in catenary-like form between said rings', each of said blades consisting of a mem- 5 ber of sheet material which is'curvilinear in section in three right angularly related planes.

'7. A blade rim for radial admission turbines comprising axially spaced rotatable blade carrying rings, and blades anchored at their endsto 50 and extending in catenary-like form between said rings, each of said blades consisting of a member of sheet material which is curvilinear in section in three right angularly related planes, the curvature of said blade middle thereof and gradually decreasing toward the blade ends. I

8. A blade rim for radial admission turbines comprising axially spaced rotatable blade carrying rings having ceiving grooves formed in the periphery thereof, and blades anchored at their ends in said grooves and extending in catenary-like form between said rings, each of said blades consisting of a member of sheet material which is curvi- 65 linear'in section in three right angularly related planes, the curvature of said blade being a maximum in the middle thereof and disappearing gradually toward the blade ends, the latter being rectilinear and thicker than the remainder of 70 the blade for retention within said grooves.

9. A blade rim for radial admission turbines comprising axially spaced rotatable blade carrying rings, and blades anchored at their ends to and extending in catenary-like formbetween said 75 and curved transversely,- 35

are catenarlan-like in character. 40

being a maximum in the 55 a series of rectilinear blade re- 60 rings, each of said blades consisting of a membet or sheet material which is curvilinear in cross section in three right angularly related planes and such that the blade angle is constant along the ventire width 01' the blade.

10. A blade rim for radial admission turbines comprising axially spaced rotatable blade carrying rings, and blades anchored at their ends to and extending in catenary-like i'orm between said rings, each of said blades consisting of a member of sheet material transversely curved so that the lines of intersection oi the blade with planes perpendicular to the axis of rotation are involute-like in character and with planes parallel to said axis are catenarian-like in character. rim for radial admission turbines comprising axially spaced rotatable blade carrying rings, and blades anchored at their ends to and extending in catenary-llke iorm between said rings, each of said blades consisting 01' a member of sheet metal transversely curved so that the lines of intersection of the blade with planes perpendicular to and parallel to the axis or rotation are involute-llke and catenary-like in form, respective the edges of said blades also curving in two directions.

12. A blade rim for radial admission turbines comprising axially spaced rotatable blade carrying rings, and a series 01' blades a ored at their ends to and extending in catenary-like iorm between said rings, each of said blades consisting of a member of sheet material which is curvilinear in cross section in three right anguiarly related planes and adjacent'blades overlapping each other throughout at least a part of the span between said rings.

13. A turbine blade comprising a plurality oi members 01' sheet material united edge to edge and having the form of a catenary-like curve between its ends and curvilinear in section in three right angularly related planes.

FR-I'I'Z ALEXANDER. WE'I'ISTEIN. 

